This project is concerned with the determination of protein conformation using the technique of X-ray crystallography. The major problem currently under investigation concerns the catalytic mechanism of the enzyme lactose synthase; a unique enzyme system formed by the interaction of a water-soluble milk protein, alpha-lactalbumin, with a membrane bound galactosyl transferase. The approach to be used involves determination of the tertiary structures of both alpha-lactalbumin and galactosyl transferase by X-ray crystallography. Significant homology in the amino acid sequences of alpha-lactalbumin and hen egg white lysozyme suggests that these two proteins have a common genetic origin. Determination of the X-ray crystal structure of alpha-lactalbumin would permit a comparison of the tertiary structures of these two proteins. This would provide an opportunity to reveal how, in one case, structural changes during evolution have given rise to a totally new biochemical function. Galactosyl transferase has been identified as a marker protein present in the serum of patients with certain types of malignant tumor. Structural studies of metabolic control of this enzyme at the molecular level could have implications for the advancement of cancer research. A second project is concerned with the structures of chlorophyll-containing proteins. The amino acid sequence of a bacteriochlorophyll-protein complex, with known tertiary structure is being determined in order to investigate the specific chemical interactions between the chlorophyll and the protein. Further studies of chlorophyll-protein interactions will involve determination of the tertiary structure of a water-soluble peridinin-chlorophyll-protein from marine dinoflagellates by X-ray crystallography. It is hoped that the results of this work will be useful in explaining the structural basis for the efficient transfer of energy between peridinin and chlorophyll in this complex. Preliminary crystallization studies on the enzymes, myeloperoxidase, AMP-deaminase and fumarse are also proposed.